Installation for burning combustible mixtures

ABSTRACT

1. A BURNER INSTALLATION FOR BURNING A PUMPABLE COMBUSTIBLE MIXTURE, SUCH AS OIL-BEARING SLUDGES OR THE LIKE, CONTAINING PARTICULATE CONTAMINANTS, COMPRISING: BURNER NOZZLE MEANS, SAID BURNER NOZZLE MEANS INCLUDING AN ELONGATE CHAMBER HAVING A NOZZLE TIP AT ONE END THEREOF, MEANS FOR SUPPLYING A CONTROLLED VOLUME OF PRESSURIZED PRIMARY AIR TO SAID CHAMBER, MEANS FOR CONVEYING A QUANTITY OF SAID SLUDGE INTO SAID CHAMBER AT A POINT ADJACENT THE END OF SAID ELONGATE CHAMBER REMOTE FROM SAID NOZZLE TIP IN PREDETERMINED CONTROLLED PROPORTION TO THE VOLUME OF SAID PRIMARY AIR, SAID CHAMBER BEING ADAPTED TO MIX SAID PRIMARY AIR AND SAID SLUDGE TO FORM A COMBUSTIBLE SLUDGE-AIR ADMIXTURE THEREIN, SAID AIR SUPPLYING MEANS COMPRISING REGULATING VALVE MEANS ADAPTED TO ADJUST THE STATIC PRESSURE HEAD OF SAID PRIMARY AIR TO VARY THE EFFECTIVE SLUDGE INLET AREA INTO SAID CHAMBER AND THEREBY REGULATE THE RATIO OF PRIMARY AIR AND SLUDGE IN SAID CHAMBER, AND SAID PRESSURE IN SAID CHAMBER BEING EFFECTIVE TO CONTINUOUSLY EFECT SAID ADMIXTURE THROUGH SAID NOZZLE TIP FROM SAID CHAMBER INTO SAID BURNER, MEANS FOR SUPPLYING A CONTROLLED QUANTITY OF PRESSURIZED SECONDARY AIR TO THE SLUDGE-AIR ADMIXTURE IN SAID CHAMBER, SAID LAST-MENTIONED MEANS COMPRISING A CHAMBER ENCOMPASSING SAID NOZZLE CHAMBER SO AS TO DEFINE AN ANNULAR PASSAGEWAY THEREBETWEEN, AND APERTURE MEANS IN THE WALL OF SAID NOZZLE CHAMBER TO FACILITATE FLOW OF SAID SECONDARY AIR FROM SAID PASSAGEWAY INTO SAID NOZZLE CHAMBER IN THE REGION OF SAID NOZZLE TIP.   D R A W I N G

United States Patent 11 1 Vier et al.

[ Oct. 8, 1974 INSTALLATION FOR BURNING COMBUSTIBLE MIXTURES [75]Inventors: Fritz Vier, Bernhard Winkeler, both of Salzbergen, Germany[73] Assignee: Wintershall Afiiengesgllschaft,

Kassel, Germany [22] Filed: Nov. 24, 1971 [21] Appl. N0.: 201,734

Related US. Application Data [62] Division of Ser. No. 100,968, Dec. 23,1970, Pat. N0.

[52] US. Cl 239/127, 239/400, 239/406, 239/419.3, 110/75 [51] Int. ClB05b 9/00, B05b 7/10, F23d 11/16 [58] Field of Search 239/124, 127, 399,400, 239/403, 405, 406, 407, 413, 416.1, 416.4,

[56] References Cited UNITED STATES PATENTS 943,385 12/1909 Bullock239/428 X 738,131 9/1903 Weaver 239/400 X 998,762 7119]] Faller 239/4031,244,329 10/1917 Hinz 239/4l6.1

1,612,457 12/1926 Marron 239/424 2,095,242 10/1937 Dick 239/4002,143,817 l/1939 Longdin et al 239/428 X 3,070,317 12/1962 Hunter et al239/403 X 3,176,921 4/1965 De Voe 239/124 X 3,357,375 12/1967 Brophy110/7 S 3,489,108 1/1970 Garver et a1 110/7 5 FOREIGN PATENTS ORAPPLlCATlONS 522,485 6/1940 Great Britain 239/399 Primary ExaminerRobertS. Ward, Jr. Attorney, Agent, or FirmWaters, Roditi, Schwartz &

Nissen [57] ABSTRACT A process and burner installation for burningcombustible waste product sludges containing solid particulatecontaminants," including a nozzle chamber adapted to mix thewaste sludgewith pressurized air. The static air pressure in the nozzle chamber ismaintained at a predetermined pressure head in order to regulate theinlet of sludge t0 the chamber, so as to thereby effect control over theratio of sludge to air in the mixture formed for burning.

6 Claims, 3 Drawing Figures PATENTED BET 1 74 sum 30F 3 INSTALLATION FORBURNING COMBUSTIBLE MIXTURES This application is a divisionalapplication of Ser. No. 100,968, filed Dec. 23, 1970 and now U.S. Pat.No. 3,659,786.

This invention relates to a process and installation for burningcombustible mixtures and, more particularly, to a process andinstallation for burning pumpable homogenized combustible mixtures suchas oily sludges or the like containing particulate contaminants.

In industry, the disposal of many types of residual or waste productscreates complex and burdensome technological problems. In particular,waste products in industries such as, for example, petroleum processingplants, oil refineries, petrochemical plants and industrialmanufacturing plants, produce large quantities of waste productscontaining dirty oil substances, oily liquid refuse, waste andemulsifier oils, organic residues such as varnishes and solvents whichform oily sludges containing solid particles, which must be disposed ofeconomically while considering the possible effects of polluting streamsand the environment in the dumping of these waste products. Furthermore,quite similar serious problems arise in the disposal of biologicalsewage, and from. the disposal of oily scum and sedimentcontainingsludges resulting from waste water clarification, particularly fromclarification processes relating to inorganic and/or organicflocculants.

FIELD OF THE INVENTION -A particularly desirable process in thetreatment of these types of residual waste products has been thecombustion or burning thereof, which will, in effect, eliminate thepollution of streams and environs into which such waste products havepreviously been poured. Although various processes and installations forthe combustion or burning of such oil-bearing, solids containing sludgeshave been heretofore proposed, these have encountered considerabletechnological problems during practical application thereof when thewaste products being burned have not been extensively pre-treated. Ineffect, in prior art processes for burning combustible waste sludges,the solid or particulate contaminants in the sludges or mixture beingburned have generally tended to clog and foul valves and shuttlecocks inthe conduits supplying the sludges, thereby adversely affecting anypracticable control or regulation of the volume and consistency of thewaste sludge material being pumped through the waste disposal system.Consequently, combustion of such sludges through prior art installationsat best has afforded to be erratic and resulted in frequently incompleteburning of the waste material.

It has also been difficult to provide installations for the completecombustion or burning of oily sludge waste products which are operativefor extensive periods of time. Since solids particulate containing wastesludges can only be burned in presently available burners providingadequate pumping pressure is supplied thereto, pumps which must providethis pressure have been subjected to undue wear and tear causingfrequent pump breakdowns, resulting from the inherent deleterious natureof the waste sludges containing the particulate contaminants, therebyrendering such waste product combustion processes and installationscostly and inefficient in operation.

It has been now proposed to provide. specialized burner installations inwhich solids containing oily sludges are burned through a processwhereby the sludges are admitted to an inner tube containing a flownozzle having relatively large dimensions. The inner tube is positionedwithin a secondary conduit which conveys combustion assisting air to thewaste sludge in a vortex stream adjacent to the ignition nozzle of theburner. Although this may provide generally satisfactory burningperformance, the quantity of sludge being burned is controlled by acomplex valve arrangement and pressure generating pump which are subjectto the wear and tear and breakdowns of earlier combustion installationsfor waste products or sludges.

In another prior art process and apparatus for burning oil-bearing,solids contaminated waste sludges, the sludges are introduced into theinner casing of a combined gas-oil burner of generally known standardtype construction. This particular burning process requires that thewaste sludges be pumped into the burner by an intricate pumping systemwherein the quantity of sludges being consumed in the burning process iscontrolled by a suitable valve arrangement. Accordingly, as in thepreviously discussed processes and installations for combusting thesludges or waste products, there is again the problem of undue wear andtear of the various components of the installation, which leads to therapid deterioration of the burning process, thereby rendering theseinstallations inefficient and resulting in an incomplete burning of thewaste sludge.

SUMMARY OF THE INVENTION The waste product or sludge burning process andinstallation according to the present invention is designed to obviatethe drawbacks and disadvantages encountered in presently used systemsfor disposing of untreated and industrial waste sludges of a combustiblenature containing solid particulate contaminants. To this effect, thepresent inventive combustion process contemplates the burning ofpumpable homogenized combustible waste mixtures containing oil-bearingsludges, which include a proportion of particulate or solid contaminantsin an unique and novel installation wherein regulated volumes ofpressurized combustion supporting air are mixed with regulatedquantities of the combustible waste sludge prior to combustion thereof,and wherein the proportions of the sludge relative to the volume of airare continuously determined and controlled by adjusting theinletpressure of the air to thereby vary the effective inlet rate or area forthe sludge into the burner installation. Consequently, by predeterminingthe pressure of the inlet air, thereby regulating the conditions underwhich the air and waste sludge are admixed prior to combustion, optimumratios between the air and the combustible waste sludge are attained atall times to effect complete and efficient burning of the combustiblesludge-air mixture.

Another feature of the present invention lies in the provision of aninstallation for effecting the combustion process for oil-bearing wastesludges as described herein, which will essentially eliminate the needfor valve and pumping elements which are subjected to undue wear andtear. In this connection, the novel installation includes a nozzlechamber arrangement whereby an oil-bearing, solid contaminantscontaining waste sludge is mixed with air to form a combustiblesludge-air admixture, and wherein the optimum ratio between the air andoil-bearing sludge is determined by the internal pressure head withinthe nozzle chamber responsive to the inlet pressure provided by the air.This installation, as may be readily ascertained, generally obviates theneed for complex pumping and valve arrangements required in prior artcombustion installations.

Accordingly, it is a primary object of the present invention to providefor a process for burning pumpable,

homogenized combustible waste product mixtures,

such as oil bearing sludges and the like which contain solidsparticulate contaminants.

Another object of the present invention is to provide a process forburning combustible waste product mixtures comprising an admixture ofsolids contaminated oil-bearing sludges and air in which the ratio ofair to the oil bearing sludge is maintained within a predetermined rangeby regulating the pressure of the air being supplied to the combustiblewaste product mixtures.

Still another object of the present invention is to provide a processfor burning combustible mixtures of homogenized oil-bearing sludgescontaining solid contaminants and including combustion supporting air,wherein the proportion of the volume of air to the quantity ofoil-bearing sludge is continuously moni tored by varying the pressurerelationship of the inlet air to the oil bearing sludge so as toregulate the input of sludge relative to the input of air.

A further object of the present invention is to provide a process forburning combustible admixtures of combustion supporting air andsolids-contaminated oilbearing waste product sludges wherein the processis carried out under controlled pressure conditions and including theaddition of a supply of a secondary combustion supporting air to enhancethe combustion properties of the combustible admixture.

A still further object of the present invention is to provide aninstallation for burning combustible homogenized mixtures of oil-bearingsolids-contaminated waste product sludges and combustion supporting airunder pre-determined conditions adapted to' maintain an optimum ratiobetween the sludges and air so as to effect complete combustion of thecombustible mixture.

A yet further object of the present invention is to pro vide aninstallation for burning solids-contaminated waste product sludgesadmixed with air under predetermined conditions, and which includespumping means for homogenizing the waste product sludges.

Yet another object of the present invention is to provide a burnerinstallation for waste products or the like including novel burnernozzle structure adapted to admix combustion supporting air andoil-bearing solids-contaminated waste product sludges under controlledpressure conditions for determining optimum air to sludge ratios so asto effect the complete and efficient burning of the admixed air andwaste sludges.

BRIEF DESCRIPTION OF THE DRAWINGS In order that the invention may bemore clearly understood and readily carried into effect, reference maynow be had to the accompanying drawings, in which:

FIG. 1 illustrates a burner nozzle and mixing chamber arrangement forcarrying out the combustion process according to the present invention;

FIG. 2 illustrates a burner installation, partially in schematic,according to the present invention; and,

FIG. 3 illustrates a modified embodiment of a burner installationaccording to the present invention.

DETAILED DESCRIPTION OF THE DRAWINGS Referring now in detail to thedrawings, wherein like reference numerals designate corresponding partsthroughout the several views, a burner nozzle and mixing chamberarrangement 1 includes a nozzle holder 2 consisting of an elongatedtubular conduit, which extends at its forward or downstream end into aburner nozzle 3. The rear or upstream end of the nozzle holder 2 extendsinto an air inlet conduit 5 through which pressurized air may beconveyed into the nozzle holder 2.

The volume and pressure of the air conveyed into nozzle holder 2 throughconduit 5 is regulated by means of a suitable control valve 4 positionedat the inlet end of conduit 5, and with the valve being connected to asuitable source of pressurized air (not shown).

A conduit 6 is adapted to convey a homogenized oilbearing waste sludgecontaining solid particulate contaminants into the upstream end ofnozzle holder 2 through an inlet aperture formed in conduit 5 adjacentthe upstream end of conduit 2. The inlet aperture for the sludge at thejuncture of conduit 5 and conduit 6 essentially defines a sludge inletarea 7 to the nozzle holder 2.

As the sludge is conveyed from conduit 6 through inlet area 7 into theupstream end 8 of nozzle holder 2, it is admixed with the pressurizedairbeing supplied through conduit 5 into nozzle holder 2. Effectively,nozzle holder 2 then becomes a mixing chamber for the air and sludge,whereby these are admixed into a combustible sludge-air mixture 9. Thesludge-air mixture 9 is continuously conveyed, under the pressureexisting within the nozzle holder 2, toward burner nozzle 3 and ejectedinto the burning chamber of a burner installation, to be described indetail herein below.

In order to enhance the combustion properties of the sludge-air mixture9, secondary air may be supplied to the mixture 9 in the region ofburner nozzle 3 prior to I ejection of the mixture into the burner. Inorder to supply the secondary air to the mixture, a duct 10! ispositioned about nozzle holder 2 so as to define an annular passagewaytherebetween. The duct 10 has a closed upstream end portion, andincludes a conduit and regulat ing valve 11 connected to a suitablesource of secondary air (not shown) which may be the same as that forthe primary air. A plurality of apertures may be provided in the wall ofnozzle holder 2 adjacent the downstream end thereof so as to receivesecondary air from the annular passageway formed between nozzle holder 2and duct 10. A plurality of diagonal vanes 12 may be positioned in theannular passageway defined by duct 10 and nozzle holder 2, in order tocreate vortex flow and agitation of the secondary air supplied throughvalve arrangement 11, which will further assist in the mixing of thesecondary air with the sludge-air mixture 9 so as to enhance thecombustion property of the air and the mixture.

The homogenized sludge conveyed into nozzle holder 2 from conduit 6 issupplied thereto under a pressure head of at least 3 meters of water,and preferably at a pressure head in the range of about 4 to 10 metersof water. Concurrently, the primary air supplied to the nozzle holder 2through conduit 5 is maintained at a static pressure head of at least 20meters of water higher than the static pressure of the sludge-airmixture 9 in the upstream region 8 of nozzle holder 2. This willregulate and vary as required the effective inlet area 7 of the sludgeentering the upstream end 8 of nozzle holder 2, thereby proportioningand defining the ratio between the volume of air entering throughconduit 5 and the quantity of homogenized sludge entering through inletarea 7 from conduit 6. By maintaining the pressure head of the airentering through conduit 5 into the nozzle holder 2 at predeterminedlevels, the effec tive inlet area 7 for the sludge may thus be varieddue to the back pressure created by the sludge-air mixture 9 in nozzleholder 2. As a result, it is possible closely to control the inletquantity of sludge passing through inlet area 7 into the upstream end 8of the nozzle holder, thereby assuring that the ratio of air to sludgeforming the combustible mixture will be maintained at optimum conditionfor complete and efficient burning of the mixture 9 when ejected fromburner nozzle 3.

Referring to the burner installation of FIG. 2 of the drawing, thenozzle arrangement 1 illustrated in FIG. 1, is shown connected to ahopper or tank 13 which receives a supply of solidparticulate-contaminated oilysludge waste material from a sewage plantor industrial installation. The tank 13 may comprise a generally conicaltank structure having an outlet conduit 14 connected to the inlet end ofa homogenizing pump 15 which sucks the solids contaminated sludge fromthe tank 13. The homogenizing pump 11, in effect, mixes and homogenizesthe sludge and solid particles therein to form a sludge mixture having asomewhat greater consistency throughout by breaking up some of the solidparticles and distributing these throughout the liquid of the sludge ina more evenly distributed suspension. The pump 15 may bear commercialmixing or wobble pump, which is adapted simultaneously to homogenize thesludge and to produce the required pressure head in excess of 3 metersof water for the sludge entering the nozzle holder 2 from conduit 6. Thehomogenized sludge mixture is then conveyed from the mixing pump 15under pressure through a return conduit 16 back into the tank 13 so asto be further mixed with additional waste products being conveyed intothe tank 13 from the sewage plants or industrial installation. This willincrease the extent of mixing and homogenizing of the sludge mixturebefore it is sucked into the mixing pump 15, thereby providing a sludgeof greater homogeniety being supplied to conduit 6 for burning.

Conduit 6 is connected into the return conduit 16 so as to enable tank13 to receive at least a portion of the homogenized sludge being pumpedfrom mixing pump 15 to pump the homogenized sludge back into tank 13.The quantity of homogenized sludge being conveyed through a conduit 6from return conduit 16 is regulated by means of a metering valve 17positioned in conduit 6.

As is shown in FIG. 2, the sludge-air mixture 9 in nozzle holder 2 isejected through burner nozzle 3 into a suitable burner constructionpreferably comprising a rotating drum 18 which will assure the completecombustion of the mixture, reducing the latter to ashes which may bereadily removed by suitable means.

The embodiment of the burner installation illustrated in FIG. 3 of thedrawings is essentially quite similar to that described with referenceto FIG. 2. In this embodiment, however, in order to afford greaterflexibility or control in supplying sludge to the nozzle holder 2 fromreturn conduit 16, a plurality of take-off conduits 6a, 6b, etc., may beconnected into return conduit 16 and joined into the common conduit 6.Each of the cut-off conduits 6a, 6b, etc., includes a metering valvearrangement 17a, 17!), etc., analogous to metering valve 17 in conduit6. Although the drawing only illustrates two branch conduits 6a, and 6b,any number as required may be utilized for connection into returnconduit 16. This will afford greater flexibility and control in tappingvarious quantities of homogenized sludge being processed through returnconduit 16 under the pressure generated by homogenizing and mixing pump15, while concurrently affording greater control over the pressure headon the sludge being fed into nozzle holder 2 through the sludge inletarea 7.

In this embodiment, a bucket conveyor system 20 is adapted to conveyquantities of homogenizable solids into the conical tank 13 for mixingwith the waste sludges contained therein. This particular aspect of theinvention is of particular significance in the petroleum processingindustry, wherein an accumulation of spent bleaching earths do notpermit the relegation thereof to a dump, or conveyance into a stream,because of the high oil and paraffin wax contents in the bleachingearths. Subsequently, the collective waste slurry or sludge andbleaching earths in the tank 13 are sucked into and through the mixingpump 15 for homogenization thereof prior to recirculation through returnconduit 16 or prior to being supplied to nozzle holder 2 through conduit6.

At times it may be advantageous to increase the solu' bility of theparaffin wax content in the bleaching earths with the waste sludgecontained in tank 13. In order to accomplish this, steam may be added tothe sludge in tank 13 by means of a suitable steam pipe 21, so as toheat the sludge mixture in tank 13 to a temperature range of about to95C., thereby increasing the homogenization properties of the solidparticlescontaining waste product sludge.

A particular aspect of the present burner process and installation liesin that it can effectively homogenize and burn oil-bearing sludgemixtures containing an oil content varying of from about 50 to percent,a water content of from 10 to 40 percent and a solids orparticulate-contaminant content of from about 0 to 10 percent.Heretofore, prior art processes and installations for burning sludgeshave been unable to successfully and economically burn mixturescontaining these particular component percentage range contents.

In addition to the foregoing, the inherent net heating 'value of thesludge-air mixture 9 ejected through burner nozzle 3 from nozzle holder2 may drop upon occasion below approximately 4,000 Kcal/Kg, which would,in effect, provide a mixture wherein combustion is no longerself-supporting upon ejection into the burner 18, and wherein thecombustion must then be supported by adding auxiliary fuel to themixture. In order to accomplish this, suitable combustion additives,comprising fuels, or similar combustible material, may be injected intothe sludge-air mixture 9 in nozzle holder 2 adjacent the region of theburner nozzle 3, through suitable fuel injection means so as to mix withthe sludge-air mixture 9 and increase its inherent heating value to apoint whereby the combustion of the mixture would be self-supporting.

Although there is no particular limitation as to the size and capacityof a burner installation for carrying out the process according to thepresent invention, it has been found that a burner having an outputcapacity of approximately 200 to 600 kilograms of sludge-air mixture perhour at a net heating value of the sludge-air mixture of 4,000 to 9,000Kcal/Kg is deemed to be economically feasible, when connected to a wastedisposal tank, corresponding to tank 13, adapted to receive wastesludges and having a capacity of 3 to 4 cubic meters. Largerinstallations, having capacities exceeding 5 tons/hr of mixtures mayalso be considered as practicable. The tank 13 includes a sump 22 at thebottom thereof in which larger non-homogenizable solids and foreignbodies in the waste sludges, such as bits of metal, can be collected andremoved from time to time by means of a slide extractor 23 so as toprevent these solids being sucked into and possibly damaging the mixingand homogenizing pump 15.

As discussed hereinabove, the process and burner installation of thepresent invention provides for the complete and efficient combustion ofpumpable solidscontaminated combustible waste sludge mixtures, includinghomogenizable waste products, which may contain bleaching earths andincluding the combination of numerous sedimentary and residual wasteproducts from industry and sewage disposal plants. These solidscontaminated sludges may consist of clarified sludges formedparticularly from biological sewage disposal and/or dirty oils andsimilar oily liquid refuse emanating from petroleum processing plantssuch as oil refineries and petrochemical oil plants; and/or salvage oilsand waste oils such as used engine oils, lubricating oils and emulsifieroils; and/or organic residues from varnish and solvent plants; and/oroily-scum sediment sludges from waste water clarification plants,particularly from clarification plants dealing with inorganic and/ororganic flocculants. These substances, all of which are satisfactorilyand completely processed and burned in accordance with the process andinstallations herein described may include sedimentary and flotationsludges from the mechanical clarification processes of oil refinerywaste waters, cyclate or sludges from the mechanical clarification ofoily refined waste waters containing ferric chloride and sedipur fillerscommercially marketed by Badische Anilin and Soda- Fabrik, Germany, andincluding muddy sludge oils and oil bleaching earths.

While there has been shown what is considered to be the preferredembodiments of the invention, it will be obvious that modifications maybe made which come within the scope of the disclosure of thespecification.

What is claimed is:

l. A burner installation for burning a pumpable combustible mixture,such as oil-bearing sludges or the like, containing particulatecontaminants, comprising:

burner nozzle means, said burner nozzle means including an elongatechamber having a nozzle tip at one end thereof;

means for supplying a controlled volume of pressurized primary air tosaid chamber;

' means for conveying a quantity of said sludge into said chamber at apoint adjacent the end of said elongate chamber remote from said nozzletip in predetermined controlled proportion to the volume of said primaryair, said chamber being adapted to mix said primary air and said sludgeto form a combustible sludge-air admixture therein;

said air supplying means comprising regulating valve means adapted toadjust the static pressure head of said primary air to vary theeffective sludge inlet area into said chamber and thereby regulate theratio of primary air and sludge in said chamber. and said pressure insaid chamber being effective to continuously eject said admixturethrough said nozzle tip from said chamber into said burner;

means for supplying a controlled quantity of pressurized secondary airto the sludge-air admixture in said chamber, said last-mentioned meanscomprising a chamber encompassing said nozzle chamber so as to define anannular passageway therebetween; and

aperture means in the wall of said nozzle chamber to facilitate flow ofsaid secondary air from said passageway into said nozzle chamber in theregion of said nozzle tip.

2. A burner installation as claimed in claim 1, including vane meansinterposed in said annular passageway so as to generate turbulent vortexflow of said secondary air into said nozzle chamber to enchance thecombustion rate of said sludge-air admixture.

3. A burner installation as claimed in claim 1, comprising;

tank means for said particulate-contaminated sludge;

pump means for homogenizing said sludge;

conduit means interconnecting the intake end of said pump means and saidtank means for conveying sludge from said tank means to said pump means,said pump means homogenizing and pressurizing said sludge;

return conduit means interconnecting the outlet of said pump means andsaid tank means to re-convey said homogenized pressurized sludge to saidtank means, and

branch conduit means including flow valve means extending from saidreturn conduit means to the sludge inlet of said nozzle chamber forconveying at least a portion of said homogenized sludge thereto undercontrolled conditions.

4. A burner installation as claimed in claim 3, including a plurality ofsaid branch conduit means interconnecting said return conduit means andthe sludge inlet of said nozzle chamber, so as to convey one or morecomponent portions of said homogenized sludge to said nozzle chamberunder controlled conditions.

5. A burner installation as claimed in claim 3, comprising;

conveying means adapted to add particulate contaminants includinghomogenizable solids, such as oily and waxy bleaching earths or thelike, to the sludge in said tank means for mixing with said sludge.

6. A burner installation as claimed in claim' 3, comprising;

means for supplying a quantity of steam to said tank means for heatingthe sludge therein to a temperature of about to C.

